Tuner for radio frequency transmission lines

Abstract

A tuner for radio frequency coaxial cable transmission lines is provided. It requires only one micrometer adjusting screw since the capacitor electrode that mates with the central conductor of the coaxial line is not only curved to give a large area in proximity to the central conductor but is rectangular and much longer than the diameter of the micrometer screw.

We claim to have invented: 
     
       1. A tuner for coaxial radio frequency transmission lines, comprising: a coaxial line of extended length, said coaxial line having a central conductor,   said coaxial line having two ends one of which may be an input for radio frequency signals and the other end may act as an output for those signals,   said outer conductor defining an elongated slit, that is parallel to said central conductor,   a tuning element movable along said elongated slit to vary the tuning of said tuner,   said tuning element having a capacitor element movable toward and away from said central conductor, to further vary the tuning of said tuning element,   said capacitor element having a generally concave shape as viewed from an end of said central conductor,   said capacitor element being the sole capacitor element, in the tuner, that moves toward and away from said central conductor.   
     
     
       2. A tuner as defined in claim 1 in which said capacitor element is substantially concentric with the center conductor in at least one of the positions that said capacitor element would have during its movement toward and away from said central conductor. 
     
     
       3. A tuner as defined in claim 2 having means for preventing rotation of said capacitor element when that element is moved toward and away from said central conductor. 
     
     
       4. A tuner as defined in claim 3 in which means prevents rotation of said capacitor element when that element is moved longitudinally in a direction parallel to said central conductor. 
     
     
       5. A tuner as defined in claim 4 in which said tuning element includes a micrometer for effecting said movement of said capacitor element toward and away from said central conductor. 
     
     
       6. A tuner as defined in claim 1 in which said signals have a wavelength, said capacitor element having a length that does not exceed one-eighth of said wavelength.   
     
     
       7. A tuner as defined in claim 1 in which said outer conductor has inductance due to said slit and means for compensating for said inductance.   
     
     
       8. A tuner as defined in claim 1 in which said capacitor element is free of sharp corners. 
     
     
       9. A tuner as defined in claim 1 in which said tuning element and said capacitor are maintained at ground potential. 
     
     
       10. A tuner for coaxial radio frequency transmission lines, including: a coaxial cable of extended length, said cable having a central conductor, and an outer conductor,   said cable having two ends one of which may be an input for radio frequency signals and the other end may act as an output for those signals,   said outer conductor defining an elongated slit, that is parallel to said central conductor,   a tuning element movable along in said elongated slit to vary the tuning of said tuner,   said tuning element also having a capacitor element movable toward and away from said central conductor to further vary the tuning of said tuning element, and   means for moving said capacitor element toward and away from said central conductor without rotating said capacitor element,   the improvement comprising: said capacitor being the sole capacitor element, in the tuner, that moves toward and away from said central conductor.     
     
     
       11. A tuner as defined in claim 10 in which said means includes a micrometer for moving said capacitor element toward and away from said central conductor. 
     
     
       12. A tuner as defined in claim 10 including means for guiding said capacitor element and preventing rotation thereof when said element is moved in a direction parallel to said central conductor. 
     
     
       13. A tuner as defined in claim 10 having means for maintaining said capacitor element at ground potential. 
     
     
       14. A tuner as defined in claim 13 having means for maintaining said outer conductor at ground potential. 
     
     
       15. A tuner for coaxial radio frequency transmission lines, comprising: a coaxial line of extended length, said coaxial line having a central conductor,   said coaxial line having two ends one of which may be an input for radio frequency signals and the other end may act as an output for those signals,   said outer conductor defining an elongated slit, that is parallel to said central conductor,   a tuning element movable along said elongated slit to vary the tuning of said tuner,   said tuning element also having a capacitor element,   a manually movable device for moving said capacitor element toward and away from said central conductor to further vary the tuning of said tuning element,   said capacitor element being long, in the direction parallel to the central conductor, as compared to the diameter of said micrometer screw, in said direction,   said capacitor element being the sole capacitor element, in the tuner, that moves toward and away from said central conductor.   
     
     
       16. A tuner as defined in claim 15 in which said elongated slit has a length, said capacitor being shorter, in a direction parallel to said slit, than said length. 
     
     
       17. A tuner as defined in claim 16 which said capacitor element is concave as viewed from an end of said central conductor. 
     
     
       18. A tuner as defined in claim 15 wherein said manually movable device incudes a micrometer for moving said capacitor element toward and away from said central conductor. 
     
     
       19. A tuner as defined in claim 15 wherein said capacitor element has a rectangular cross section in a plane parallel to said central conductor, said rectangle having its longer sides parallel to said central conductor. 
     
     
       20. A tuner as defined in claim 19 in which said radio frequency signals have a wavelength, said longer sides being no longer than 1/8 of said wavelength.   
     
     
       21. A tuner as defined in claim 15 having means for maintaining said tuning element and said capacitor element at ground potential.